PMDC SERVO MOTOR WITH quadrature encoder DRIVE ?

[phoenix_1]

Hi mackrackit and Henrik,
My PIC is 18F4431
I have success with 20MHz XTAL and define osc 20 , fuse HS.
I found motor with encoder with INDEX pin and little modific Hanrik code.
Result is 16 bit counter but I must find calculation becouse my encoder is 500 pulse per full rev of motor shaft.
Henrik you was give me good way for start with 18F4431..thanks man again.

[mackrackit]

Hi mackrackit,
My PIC is 18F4431
I have success with 20MHz XTAL and define osc 20 , fuse HS.

Mine works fine with 20Mhz HS also. It is when I try to run at 40Mhz HSPLL the problem starts. Maybe I have some bad 10s that are running a bit fast???
I have some new 10Mhz on order, find out then.

[HenrikOlsson]

Hi,
Again, you don't have to use the index channel, it'll work fine without it. If you set up the QEI module to reset on index (as in my example) and the encoder doesn't have an index channel the counter will simply roll over from $FFFF to $0000 or from $0000 to $FFFF depending on direction. Carefully read the section of the datasheet, play with it a bit and read the datasheet again, you'll figure it out ;-)

/Henrik.

[phoenix_1]

Hi,
Again, you don't have to use the index channel, it'll work fine without it. If you set up the QEI module to reset on index (as in my example) and the encoder doesn't have an index channel the counter will simply roll over from $FFFF to $0000 or from $0000 to $FFFF depending on direction. Carefully read the section of the datasheet, play with it a bit and read the datasheet again, you'll figure it out ;-)

/Henrik.

Yes I was read that part a couple of time and again and again...
How I see that full 18F4431 is extra MCU and most of you must do is to set
tons of nibbles on config registers but!
If you do that right you will have pleasure to use many finished hardware periferials without to much programing...inside 18F4431 is so many good things...

Regards Robert

[mackrackit]

Hi,
Again, you don't have to use the index channel, it'll work fine without it. If you set up the QEI module to reset on index (as in my example) and the encoder doesn't have an index channel the counter will simply roll over from $FFFF to $0000 or from $0000 to $FFFF depending on direction. Carefully read the section of the datasheet, play with it a bit and read the datasheet again, you'll figure it out ;-)

/Henrik.

Hi Henrik,
I do not have an encoder to play with but I might some day
Reading through all of this I am not seeing how the count will go up or down depending on the direction.

Would you mind enlightening me?

[HenrikOlsson]

Hi,
The encoder outputs channels which has a 90° phase shift between them.

The QEI-module can be set to 2X or 4X mode (X4 is the most common) but the easiest to understand is the 1X mode....

Simply, if the B channel is high on the rising edge of the A channel then you count up, if the B channel is low on the rising edge of the A channel then you count down. In 2X mode you "trig" on the rising edge of both channels (giving you a resolution of 2X the line count of the encoder) and it 4X mode you trig on the rising AND falling edge of BOTH channels (giving you a resolution of 4X the line count of the encoder).

If you look up incremental or quadrature encoder on Wikipedia you'll find more details.

/Henrik.

[mackrackit]

Thanks Henrik,

I understand now.

[phoenix_1]

Now I am probe on many ways to do next but I cant to image how.
1. I was setup count for QEI with friends from these forum to count from 0 - 12500 - becous my motor have gear 6.25:1 and 6.25*2000 = 12500(reding of one turn of motor shaft with 500 lines encoder) give me full 360' of output shaft range.That work extra.
Next : If I want to move for example 1mm on my mechanic I need one turn of output shaft that give me easi to control position of count from CW 0-12500 or CCW 12500 to 0.That is all in 16bit counter.
But what if I need to move more then 16bit counter ?
OK I can use PBPL and define 32bit variable - I was probe and it work 100%.
I can easy set to se if X VAR LONG number 25000000 that give me 25000000/12500 = 2000mm - inpresive!
But how I can my software variable defined as LONG from 0 - 25000000 to increment or decrement from hardware COUNT buffer wich count in circle from 0-12500 and vice verse ?
Is any idea becouse all what I was probe give me garbage of result.

Regards Robert